Power bank



FIG. 1 is a front elevational view of a power bank showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a top, front, left side perspective view thereof;

FIG. 8 is a top, rear, right side perspective view thereof; and,

FIG. 9 is a bottom, rear, left side perspective view thereof.

The broken lines in the drawings depict portions of the power bank that form no part of the claimed design. 

CLAIM The ornamental design for a power bank, as shown and described. 